This invention relates to an ink jet printhead chip. More particularly, the invention relates to an ink jet printhead chip and a method of manufacturing an inkjet printhead chip.
As set out in the material incorporated by reference, the Applicant has developed ink jet printheads that can span a print medium and incorporate up to 84 000 nozzle assemblies.
These printheads include a number of printhead chips. One of these is the subject of this invention. The printhead chips include micro-electromechanical components that physically act on ink to eject ink from the printhead chips.
The printhead chips are manufactured using integrated circuit fabrication techniques. Those skilled in the art know that such techniques involve deposition and etching processes. The processes are carried out until the desired integrated circuit is formed.
The micro-electromechanical components are by definition microscopic. It follows that integrated circuit fabrication techniques are particularly suited to the manufacture of such components. In particular, the techniques involve the use of sacrificial layers. The sacrificial layers support active layers. The active layers are shaped into components. The sacrificial layers are etched away to free the components.
Cost is a major factor in approving the manufacture of such devices. Cost is primarily dependent on the number of steps required to fabricate the device. Fabrication of mask sets is a one-off task. However, an extra step in an industrial process will have to be repeated many thousands of times. It follows that it is important for a fabrication process to incorporate as few steps as possible.
Applicant has conceived this invention to achieve such a process. In particular, the Applicant has devised a printhead chip that requires a reduced number of fabrication steps.
According to a first aspect of the invention, there is provided a method of fabricating a printhead chip for an ink jet printhead the printhead chip including a plurality of nozzle assemblies positioned on a wafer substrate that incorporates a drive circuitry layer, each nozzle assembly having nozzle chamber walls and a roof that define a nozzle chamber and an ink ejection port and an actuator, connected to the drive circuitry layer, that is operatively positioned with respect to the nozzle chamber to act on ink within the nozzle chamber to eject the ink from the nozzle chamber, the method comprising the steps of:
depositing a first sacrificial layer on the wafer substrate;
etching the first sacrificial layer to form a deposit area for an actuator layer;
depositing actuator material on the first sacrificial layer to form the actuator layer;
etching the actuator layer to define the actuator and a first part of the nozzle chamber walls of each nozzle assembly;
etching the first sacrificial layer to release each actuator and each first part of the nozzle chamber walls; and
etching at least one of the wafer substrate and the first sacrificial layer to define a plurality of ink inlets, so that each ink inlet is in fluid communication with a respective nozzle chamber.
The method may include the steps of:
depositing a second layer of sacrificial material on the actuator layer;
etching the second layer of sacrificial material to form a deposit area for a structural layer;
depositing structural material on the second layer of sacrificial material to form the structural layer; and
etching the structural layer to form a second part of the nozzle chamber walls of each nozzle assembly, the steps of depositing the first and second layers of sacrificial material, the actuator material and the structural material and etching the sacrificial material, the actuator material and the structural material being carried out so that the first and second parts of the nozzle chamber walls define a fluidic seal between the first and second parts when the nozzle chamber is filled with ink.
The steps of depositing the first and second layers of sacrificial material, the actuator material and the structural material and etching the sacrificial material, the actuator material and the structural material may be carried out so that the structural material defines the roof wall in addition to said second part of the nozzle chamber walls and the ink ejection port defined in the roof wall.
The steps of depositing the first and second layers of sacrificial material, the actuator material and the structural material and etching the sacrificial material, the actuator material and the structural material may be carried out so that the first part of the nozzle chamber walls is fast with the substrate, while the second part is connected to the actuator to be displaceable towards the first part to reduce a volume of the nozzle chamber to eject ink from the ink ejection port and away from the first part to refill the nozzle chamber.
According to a second aspect of the invention, there is provided a printhead chip for an inkjet printhead, the printhead chip comprising
a wafer substrate;
a drive circuitry layer positioned in the wafer substrate;
a plurality of nozzle assemblies positioned on the wafer substrate, each nozzle assembly comprising
nozzle chamber walls and roof walls that define a plurality of nozzle chambers and ink ejection ports, each ink ejection port being in fluid communication with a respective nozzle chamber; and
a plurality of actuators connected to the drive circuitry layer, each actuator being operatively positioned with respect to a corresponding nozzle chamber so that each actuator can act on ink within a respective nozzle chamber to eject the ink from that nozzle chamber, the actuator and a first part of the nozzle chamber walls both constituting actuator material; and
one of the wafer and nozzle chamber walls defining an ink inlet in fluid communication with the nozzle chamber.
The first part of the nozzle chamber walls may be fast with the substrate. A second part of the nozzle chamber walls and the roof walls may each connected to respective actuators to be displaceable towards the substrate to reduce a volume in each nozzle chamber to eject ink from the ink ejection port and away from the substrate to refill the nozzle chamber.
The first and second parts of the nozzle chamber walls may be shaped to define a fluidic seal to inhibit the egress of ink from the nozzle chambers when the first and second parts of the nozzle chamber walls are displaced with respect to each other.
Each actuator may be elongate with one end anchored to the substrate in electrical connection with the drive circuitry layer and an opposed end connected to the second part of the nozzle chamber walls and roof wall. The actuator may be of a material and may be configured so that the actuator is displaced towards the substrate when heated and away from the substrate when cooled, to displace the actuator and thus the nozzle chamber walls and roof wall towards and away from the substrate.
Two beams may constitute the thermal bend actuator, one being an active beam and the other being a passive beam. By xe2x80x9cactive beamxe2x80x9d is meant that a current is caused to flow through the active beam upon activation of the actuator whereas there is no current flow through the passive beam. It will be appreciated that, due to the construction of the actuator, when a current flows through the active beam it is caused to expand due to resistive heating. Due to the fact that the passive beam is constrained, a bending motion is imparted to the connecting member for effecting displacement of the nozzle.
The beams may be anchored at one end to an anchor mounted on, and extending upwardly from, the substrate and connected at their opposed ends to a connecting member. The connecting member may comprise an arm having a first end connected to the actuator with the second part of the nozzle chamber walls and the roof wall connected to an opposed end of the arm in a cantilevered manner. Thus, a bending moment at said first end of the arm is exaggerated at said opposed end to effect the required displacement of the second part of the nozzle chamber walls and roof wall.